Transducer



United States Patent 3,096,691 TSDUCER Clarence P. Salmon, Eigin, Illassignor to Flexonics (Iorporation, Maywood, llL, a corporation ofIllinois Filed June 27, 1960, Ser. No. 38,924 6 Claims. (Cl. 92-101).

This invention relates generally to transducers and especially totransducers of the type adapted to convert fluid expansion to linearmechanical movement.

Transducers of the type described commonly utilize an elastomericelement for converting the volume expansion of a thermally responsivematerial to the linear motion of a piston. One frequently employedarrangement calls for the elastomeric element to define a blind borewhich receives a portion of the piston. In this arrangement, expansionof the thermally responsive material causes the piston to be squeezedpartially out of the blind bore. Elastomeric elements of this type,while oflering great utility, have proved expensive to manufacturebecause their complex shape requires molding or other, no less costly,production methods.

An alternative scheme calls for use of a simple, flat diaphragminterposed between the expansible material and the piston; and althoughstructures of this general nature avoid expensive, molded rubber parts,they have heretofore exhibited unduly short cycle-life, failure of thediaphragm ordinarily occurring before thirty-thousand cycles have beencompleted.

Therefore, an important object of the present invention is to provide atransducer which employs a simple, flat elastomeric element whileexhibiting extended cycle-life.

A more general object of the invention is to provide a new and improvedtransducer of the type which is adapted to convert fluid expansion tolinear mechanical movement.

Another object of the invention is to provide a transducer which issusceptible of substantial minaturization.

Yet another object of the invention is to provide a transducer which iseconomical to manufacture.

A further object of the invention is to provide a transducer whichdisplays a low hysteresis lag.

Additional objects and features of the invention pertain to theparticular structure, arrangements and materials whereby the aboveobjects are attained.

A structure in accord with the invention includes a cupshaped housing, afitting confined in the housing by deforming the edges of the open endof the housing thereover, an elastomeric disc situated in the housingbeneath the fitting, a sleeve bearing defined in the fitting anddisposed perpendicularly to the disc, a piston means slidably receivedin the sleeve bearing and displaying an anti-friction surface to oneside of the disc, and means in the housing communicating an expansiblefluid to the opposite side of the disc.

The invention, both to its structure and mode of operation, will bebetter understood by reference to the following disclosure and drawingforming a part thereof, wherein:

FIG. 1 is an enlarged, side-elevational view partially in cross-sectionof a transducer constructed in accordance with the present invention andshowing the piston in its retracted position;

FIG. 2 is a view similar to the showing of FIG. 1 but omitting theshowing of the sensing bulb and illustrating the piston in its extendedposition;

FIG. 3 is a showing similar to FIG. 2 illustrating a modified transducerconstructed in accordance with the invention;

FIG. 4 is another showing similar to FIG. 2 of a further modifiedembodiment of the invention; and

3,696,691 Patented July 9, 1963 FIG. 5 is a perspective view of theelastomeric disc used in the transducer of the invention.

Referring now in detail to the drawing, specifically to FIGS. 1 and 2, atransducer indicated generally by the numeral 10 will be seen embodiedin a thermostatic device, the transducer 10 being particularly connectedto a sensing bulb 12 by means of a capillary tube 14. The transducer 10will "be seen to include a cup-shaped housing 16, the open end of whichis defined by deformable lips 18. A fitting 20 is confined within thehousing 16 by crimping the lips 18 over flange portions 22 of thefitting. In accordance with the invention, an elastomeric disc 24 issituated in the housing 16 beneath the fitting 20; and as will be noted,the crimping over of the lips 18 is adapted to compress the peripheralportions of disc 24 between the flange portions 22 of fitting 2t] andthe floor of housing 16. Thus, the transducer is sealed against leakage.

With reference for the moment to FIG. 5, the elastomeric disc 24 will beseen to take the shape initially of a cylinder possessing a radiussubstantially in excess of its height. In other words, the disc 24 is,initially, substantially flat; and accordingly, it may be fabricated bydie cutting or blanking from vulcanized sheet stock. Considerableeconomies in manufacture can thus be realized. Returning to FIG. 1, itwill be observed that the disc 24 is compressed to approximatelyone-half its thickness at the periphery beneath flange portion 22whereas the central portion of the disc 24 remains unstressed.

The fitting 20 is arranged to define a sleeve bearing 26 which opensperpendicularly from disc 24; and in accordance with an importantfeature of the invention, a piston 28 is slidably received into thesleeve bearing 26 to display an anti-friction surface 30 to the disc 24.In the specific embodiment of the invention shown in FIGS. 1 and 2, theentire piston 28 is fabricated from polytetrafluoroethylene resin inorder to establish the proper antifriction surface.

An expansible fluid 32 is contained within the sensing bulb 12, withinthe capillary tube 14 and within a hollowed portion 34 of housing 16,portion 34 being arranged to communicate the fluid 32 to one side ofdisc 24. Since, for the embodiment of FIGS. 1 and 2, the transducer 10is selected to be a component of a thermostatic device, increasing thetemperature of the sensing bulb 12 will cause a thermal expansion of thefluid 32; and this expansion will be realized within the transducer 10by an extension of disc 24 as is well shown in FIG. 2, there being aconcomitant linear displacement of piston 28.

In accordance with an important feature of the invention, the edges 36of sleeve bearing 26 are rounded adjacent disc 24 to facilitateextension of the disc thereover. Moreover, it has proved advantageous toprovide relieved shoulder portions 38 in the sleeve bearing 26 radiallyinwardly from the flange portions 22. The relieved shoulders 38 alsofacilitate extension of the disc 24.

With continuing reference to FIG. 2, it will be observed that theelastomeric disc 24 is substantially stressed when the piston 28 hasbeen displaced outwardly by expansion of the fluid 32. The stresses thusimposed on the clastomeric disc 24 tend to return the disc to itsinitial position upon contraction of the fluid 32, as might beexperienced upon cooling of sensing bulb 12. The customarily provided,external spring loading of piston 28 also cooperates in returning thecomponents of the transducer 10 to their initial position uponcontraction of the fluid 32.

Housing 16 may be advantageously fashioned by machining, extrusion orstamping operations employing such common materials as copper, brass,bronze and steel. Fitting 26 may be likewise suitably formed. The fluid32 may be of any suitable type and preferably exists in its liquid phasethroughout the operating temperature range of the device in which it isto be utilized. Moreover, fluid 32 is desirably selected to bechemically inert to the elastomeric disc 24 'as well as to the othercomponents into which it comes in contact. Silicon oils and polyglycolshave proved eminently suitable for use as the fluid 32. In specificembodiments of the invention, disc 24- has been advantageously fashionedfrom synthetic rubber of the acrylonitrile type. V I v Turning now toFIG. 3, the capillary tubing 14 will be seen connected to a modifiedtransducer 100. Specifically, capillary tubing 14 is arranged tocommunicate with a flaring cavity 102 defined in a disc-shaped fitting104. Cavity 102 opens against one side of an elastomeric disc 1% whichis confined between the fitting 1M and the floor of a housing 108 as bycrimping the lips 110 of housing 108 over the edges of fitting 104.

The housing 108 is arranged to provide a sleeve bearing 112 in which apiston 114 is slidablyreceived. The sleeve bearing 112 defines roundededges1 16' adjacent the disc 106, rounded edges 116 being similar to therounded edges 36 of the embodiment shown in FIGS. 1 and 2. Sleevebearing 112, in addition, defines relieved shoulder portions 118 whichare similar to the relieved shoulder portions 38 of the embodiment ofFIGS. 1 and;2.

Piston 114 is desirably fabricated from polytetrafiuoroethylene resin inorder to provide the proper anti-friction surface in abutment with thedisc 108; and the other components of the transducer 100 are constructedin a similar manner and from materials similar to the correspondingcomponents of the embodiment of FIGS. 1 and 2.

In FIG. 4, a further modified form of the transducer is shown. There, atransducer 100a incorporates a piston 120 which is fabricated fromsteel; and a polytetrafiuoroethylene resin washer 122 is interposedbetween piston 120 and the elastomeric disc 106a. Furthermore, thecapillary tube 14 communicates the eXpansible fluid 32 to one side ofthe disc 106a by means of a cylindrical cavity 124. In other respectsthe transducer 100a is constructed similarly to the transducer 100; andaccordingly, like numerals have been used to designate like elements,the suflix letter a being employed to distinguishthose elementsassociated with the transducer 100a.

While particular embodiments of the invention have been shown, it shouldbe understood, ofcourse, that the invention is not limited thereto sincemany modifications may be made; and it is, therefore, contemplated tocover by the appended claims any such modifications as fall within thetrue spirit and scope of the invention.

The invention is claimed as follows:

1. A transducer adapted to convert fluid expansion to linear mechanicalmovement, said transducer comprising: cup-shaped housing means havingdeformable lips at the open end thereof; fitting means confined in saidhousing means by deforming said lips thereover; an elastomeric discsituated in said housing means beneath said fitting means; a sleevebearing defined in one of said first and second mentioned means anddisposed perpendicularly to said disc; piston means slidably received insaid sleeve bearing and displaying an anti-friction surface to one sideof said disc; and means in the other of said first and second mentionedmeans communicating an expansible fluid to the opposite side of saiddisc.

2. A transducer according to claim 1 wherein said piston means includesa metal piston member and a polytetrafiuoroethylene washer elementdisposed between said piston member and said disc.

, 3. A transducer according to claim 1 wherein said piston means isfabricated from polytetrafiuoroethylene resin.

4. A transducer according to claim 1 wherein said sleeve bearing definesa rounded edge adjacent said disc.

5. A transducer according to claim 1 wherein said sleeve bearing definesrelieved shoulder portions adjacent said disc.

6. A transducer adapted to convert fluid expansion to linear mechanicalmovement, said transducer comprising: cup-shaped housing means havingdeformable lips at the open end thereof; fitting means confined in saidhousing means by deforming said lips thereover; an elastomeric discsituated in said housing means beneath said fitting means; a sleevebearing defined in one of said first and second mentioned means anddisposed perpendicularly to said disc, said sleeve bearing defining arounded edge and relieved shoulder portions adjacent said disc; pistonmeans slidably received in said sleeve bearing and fabricated frompolytetrafiuoroethylene resin to display an anti-friction surface to oneside of said disc; and means in the other of said first and secondmentioned means communicating an expansible fluid to the opposite sideof said disc.

References Cited in the file of this patent UNITED STATES PATENTS2,534,497 Albright Dec. 19, 1950 2,913,904 Baker Nov. 24, 1959 2,931,390Vernet Apr. 5, 1960

1. A TRANSDUCER ADAPTED TO CONVERT FLUID EXPANSION TO LINEAR MECHANICALMOVEMENT, SAID TRANSDUCER COMPRISING: CUP-SHAPED HOUSING MEANS HAVINGDEFORMABLE LIPS AT THE OPEN END THEREOF; FITTING MEANS CONFINED IN SAIDHOUSING MEANS BY DEFORMING SAID LIPS THEREOVER; AN ELASTOMERIC DISCSITUATED IN SAID HOUSING MEANS BENEATH SAID FITTING MEANS; A SLEEVEBEARING DEFINED IN ONE OF SAID FIRST AND